Agreed to 60 hp. And rapid repair once reattached. Sure.
Mental Detachment (Ex): 1d4 rounds after an arcanosheen falls victim to a continuing mind-affecting effect, its organic bellypod automatically ejects from its body. This breaks the mind-affecting effect on the arcanosheen, which then behaves precisely as a render would and loses its spellcasting ability. The bellypod is effectively an object with 60 hp and hardness 1. After the end of the duration of the mind-affecting effect (acting on the bellypod), the arcanosheen may reattach the bellypod as a full-round action. The arcanosheen then regains its spellcasting ability, losing one level of spells for each round the bellypod is detached (hence, if it is detached for 13 rounds, it can lose one 7th and once 6th level spell, one 5th and four 2nd level spells, etc), and the bellypod benefits from the sheen's rapid repair ability from that time. If the pod is destroyed, the arcanosheen must return to the cyst to have a new one created.
Happy with that?